Pressure control device

Abstract

A pressure control device controls a pressure of fuel supplied from a fuel tank to an engine via a fuel pump. The pressure control device includes a valve device, a first force-applying device and a second force-applying device. The valve device is provided in a path of the fuel from the fuel pump to the engine and comprising a valve and a spring. The valve is movable in an opening direction and a closing direction for permitting and preventing flow of the fuel from the fuel pump to the engine, respectively. The spring applies a first force to the valve in the closing direction. The first force-applying device is operable to apply a second force to the valve in the opening direction depending on the pressure of the fuel supplied from the fuel pump. The second force-applying device is operable to apply a third force to the valve in the opening direction independently of the second force applied by the first force-applying device or independently of the pressure of the fuel used for the first force-applying device.

What is claimed is: 
     
       1. A pressure control device for controlling a pressure of fuel supplied from a fuel tank to an engine via a fuel pump, comprising:
 a fuel storage chamber capable of storing fuel pressurized by the fuel pump; 
 a valve seat provided at an outflow port of the fuel storage chamber, from which the fuel stored in the fuel storage chamber outflows; 
 a valve movable in a first direction toward the valve seat and a second direction away from the valve seat, wherein the valve can close the outflow port when the valve is seated on the valve seat, and the valve can open the outflow port when the valve is positioned away from the valve seat; 
 a biasing spring applying a first force to the valve in the first direction; 
 a valve opening device applying a second force to the valve in the second direction based on a pressure of the fuel stored in the fuel storage chamber; and 
 a pressure load applying device applying a third force to the valve in the second direction; 
 wherein a pressure of the fuel supplied to the engine is controlled based on the relationship between the first, second and third forces; and 
 wherein the pressure load applying device is arranged on a same side as the fuel storage chamber with respect to the valve, so that the third force of the pressure load applying device is applied only in the second direction. 
 
     
     
       2. The pressure control device as in  claim 1 , wherein the pressure load applying device comprises a pressure accumulating chamber that can accumulate a pressure for application to the valve. 
     
     
       3. The pressure control device as in  claim 1 , wherein the pressure load applying device further comprises a plunger capable acting on the valve, and the pressure accumulated within the pressure accumulating chamber is applied to the valve via the plunger. 
     
     
       4. The pressure control device as in  claim 3 , further comprising a plunger accommodating chamber movably accommodating the plunger, wherein the plunger accommodating chamber communicates with the pressure accumulating chamber, so that the pressure of the pressure accumulating chamber is applied to the plunger via the plunger accommodating chamber. 
     
     
       5. The pressure control device as in  claim 3 , wherein the plunger has a contact area for contacting the valve and a pressure receiving area for receiving the pressure of the pressure accumulating chamber, and wherein the pressure receiving area is larger than the contact area. 
     
     
       6. The pressure control device as in  claim 3 , wherein the plunger is integrally formed with the valve. 
     
     
       7. The pressure control device as in  claim 3 , wherein the plunger comprises a ball plunger. 
     
     
       8. The pressure control device as in  claim 3 , wherein the plunger is movably received within a tubular portion defining therein the pressure accumulation chamber. 
     
     
       9. The pressure control device as in  claim 8 , wherein the plunger is slidably received within the tubular portion, and a portion on the side of the plunger of the valve is also slidably received within the tubular portion. 
     
     
       10. The pressure control device as in  claim 8 , wherein the plunger is movably supported within the tubular portion via a diaphragm separating the pressure accumulation chamber from the other space within the tubular portion. 
     
     
       11. The pressure control device as in  claim 2 , wherein the pressure accumulating chamber includes an expandable portion that can expand by the pressure accumulated within the pressure accumulating chamber for applying the third force to the valve. 
     
     
       12. The pressure control device as in  claim 11 , wherein the expandable portion comprises a resilient member fitted to an open end of the pressure accumulating chamber for closing the open end. 
     
     
       13. The pressure control device as in  claim 11 , wherein the expandable portion comprises a bellows fitted between the valve and an open end of the pressure accumulating chamber opposed to the valve. 
     
     
       14. The pressure control device as in  claim 2 , wherein the pressure accumulating chamber accumulates a pressure of the fuel pressurized by the fuel pump. 
     
     
       15. The pressure control device as in  claim 14 , further comprising a control valve capable of controlling the pressure of the fuel supplied to the pressure accumulating chamber from the fuel pump. 
     
     
       16. The pressure control device as in  claim 1 , wherein the first, second and third forces are determined such that:
 (a) when a pressure within the fuel storage chamber is lower than a first predetermined pressure, the valve is seated on the valve seat by the first force, so that the fuel within the fuel storage chamber does not outflow from the fuel storage chamber; 
 (b) when the pressure within the fuel storage chamber is equal to or higher than the first predetermined pressure, the valve is positioned away from the valve seat by the second force against the first force; and 
 (c) when the pressure within the fuel storage chamber is a second predetermined pressure lower than the first predetermined pressure, the third force can be applied to the valve, so that the valve is positioned away from the valve seat by the sum of the second force and the third force against the first force. 
 
     
     
       17. A pressure control device for controlling a pressure of fuel supplied from a fuel tank to an engine via a fuel pump, comprising:
 a valve device provided in a path of the fuel from the fuel pump to the engine and comprising a valve and a spring, the valve being movable in an opening direction and a closing direction for permitting and preventing flow of the fuel from the fuel pump to the engine, respectively, and the spring applying a first force to the valve in the closing direction; 
 a first force-applying device operable to apply a second force to the valve in the opening direction depending on the pressure of the fuel supplied from the fuel pump; and 
 a second force-applying device operable to apply a third force to the valve in the opening direction independently of the second force applied by the first force-applying device; and 
 wherein the second force-applying device is arranged on a same side as the first force-applying device, so that the third force of the second force-applying device is applied only in the opening direction. 
 
     
     
       18. The pressure control device as in  claim 17 , wherein:
 the second force-applying device comprises a pressure accumulation chamber that can accumulates the pressure of the fuel supplied from the fuel pump. 
 
     
     
       19. The pressure control device as in  claim 18 , wherein:
 the second force-applying device further comprises a pressure control valve provided between the pressure accumulation chamber and the fuel pump. 
 
     
     
       20. The pressure control device as in  claim 18 , wherein
 the first force-applying device comprises a diaphragm connected to the valve and receiving the pressure of the fuel from the fuel pump.